Tensile Properties in β-Modified Isotactic Polypropylene

Spherulitic isotactic polypropylenes (iPPs) having a wide range of β-phase contents were prepared by adding β-nucleators, and the effects of the β-phase modification on the mechanical properties of the iPP were investigated. This chapter described the tensile properties of β-nucleated iPP, while key structural parameters, such as spherulite size and crystallinity, were controlled. The increase in the β-phase content led to broader yield peaks and an enhancement in the yield toughness but to a reduction in the yield strength. On the other hand, the initial elastic modulus was found to be independent of the β-contents. Furthermore, the deformation of the β-spherulites, which have a sheaflike structure, was anisotropic and depended on the stretching direction with respect to the sheaf axis. Consequently, the improved drawability and ductility of β-iPP compared to α-iPP are thus associated with the enhanced toughness resulting from the multiple deformation processes in the sheaflike spherulites

Mechanical Properties of Plasticized Cellulose Ester Films at Room and High Temperatures

Cellulose ester is a biomass-derived material and exhibits excellent heat resistance and high transparency, properties required for optical film application. Recently, attention has been paid to cellulose esters due to their potential application as a functional film. Some cellulose esters such as cellulose acetate propionate (CAP) show extraordinary dispersion of orientation birefringence, in which the birefringence increases with increasing wavelength, a property required as a retardation film. The similar behaviour is also observed for cellulose triacetate (CTA) plasticized with tricresyl phosphate (TCP). In this study, the mechanical properties of pure and plasticized CAP and CTA at room and high temperatures are investigated to relate with their birefringence property. At room temperature, CTA film shows a higher brittleness than CAP film. At 15 K above their respective Tg, pure CAP and CTA can be stretched to draw ratio of 5.0 and 2.0, respectively. However, the addition of TCP slightly decreases the stretchability in both CAP and CTA to draw ratio of 4.5 and 1.5, respectively. The stretchability of both pure and plasticized CAP and CTA is found to increase with the increase of stretching temperature, which is useful to increase the value of orientation birefringence as it increases with draw ratio. However, birefringence value becomes lower at higher temperature. Thus, to obtain an optimum value of orientation birefringence, a balance between the draw ratio and stretching temperature has to be considered

水素結合を有する低分子によるカーボンブラック充てん高分子複合材料の導電性制御

本研究は、この複合導電材料の方位に着目して、極性低分子化合物の水酸基と、樹脂がもつ酸素基との間に水素結合を形成させることにより、その場で低分子粒子を高分子マトリックスに分散させ、低分子の形や大きさなどにより導電性を支配する因子を割り出すことを行った。その導電性と直接関わる基礎的な知見を得るために、上記の導電性と密接に関係する極性低分子と高分子との水素結合に基づく分子間相互作用を明らかした。極性低分子としてヒンダードフェノールやヒンダードアミン等の極性低分子との混合系を調べた結果、マトリックス樹脂を極性低分子の間の水素結合が発生し、水素結合が分子運動性に大きく、影響を及ぼし室温領域に巨大な緩和分散を発現させることがわかった。また、延伸過程中で水素結合の組換えがおこり材料の運動性が変化することも分かった。その結果、水素結合の強弱によって分子運動性が大きく影響され、さらにはバルクの力学特性に大きく影響を及ぼすことが分かった。さらに、シリカゲルを分散材として用いた場合の分散状態と分子運動性の変化を調べた。この分子運動性は導電性と密接に関係する。シリカ微粒子と塩素化ポリエチレンが熱処理によって化学結合することがわかった。これは、これまでの水素結合により強い分散材とさらに母体材料として結晶性高分子固体であるポリプロピレンをもちいシリカゲル微粒子のとマトリックスとの相互作用をもった複合材料になることが判明した。以上の結果より、これまでほとんど困難であった樹脂の分子運動性や極性分散在の凝集状態を制御できることがわかった。今後、この成果を基礎知見として導電性のみならず応力の伝播機構やガス透過機構などの輸送現象全般の制御方法への展開を予定している。Dynamic mechanical properties and microstructure of an organic hybrid consisting of chlorinated polyethylene(CPE) and inorganic fillers such as carbon blacks, hindered phenol, hindered amine, and silica particles with some polar groups were investigated. In order to clarify the effects of hydro bond on molecular mobility of CPE, the hindered phenol and amine were added to CPE matrix. The fillers clearly exhibited two second-order transitions at 6 and 69℃ in addition to the melting : the transition at lower temperature is assigned to the glass transition. and the transition at higher temperature is considered to be caused by the dissociation of hydrogen bond between the hydroxyl groups of the fillers. When blending with CPE, part of the fillers molecules was dispersed into the CPE matrix, and most of them formed an filler-rich phase. As a result, a novel transition appeared above the glass-transition temperature of the CPE matrix. It was assigned to the dissociation of the intermolecular hydrogen bond between the a-hydrogen of CPE and the hydroxyl groups of fillers within the AO-80-rich phase. Dynamic mechanical properties and microstructure of CPE/filler hybrid were capable of being controlled by the thermal treatment. Consequently, the CPE/filler hybrid is a good damping material and shows a shape memory effect.研究課題/領域番号:13650746, 研究期間(年度):2001-200

Rheo-optical Raman study of microscopic deformation in high-density polyethylene under hot drawing

In situ observation of the microscopic structural changes in high-density polyethylene during hot drawing was performed by incorporating a temperature-controlled tensile machine into a Raman spectroscopy apparatus. It was found that the load sharing and molecular orientation during elongation drastically changed at 50°C. The microscopic stress of the crystalline chains decreased with increasing temperature and diminished around 50°C. Moreover, the orientation of the crystalline chains was greatly promoted above 50°C. These microscopic structural changes were caused by the thermal activation of the molecular motion within lamellar crystalline chains owing to the onset of relaxation of the crystalline phase. © 2015 Elsevier Ltd. All rights reserved.Embargo Period 24 month

高分子材料の破壊・破損の瞬間における分子鎖のダイナミックス

メチレンユニット数の異なる一連の直鎖状アルカンの近赤外(NIR)吸収スペクトルを評価することで、主鎖のメチレン由来のC-H伸縮振動と末端のメチル基由来のC-H伸縮振動の吸収ピークを帰属した。また、分岐状態の異なる各種ポリエチレンにおいても末端メチル基由来の振動吸収ピークを評価できることがわかった。さらに、ポリエチレンの溶融過程のNIR吸収スペクトル測定を行うことで、結晶相、非晶相それぞれの吸収ピークへの寄与を明らかにした。以上の帰属に基づき、昨年度製作した装置を用いて、一軸延伸過程中の各種ポリエチレンの分子振動状態をその場観察した。すべての試料において、降伏後のネック発現領域で、結晶相由来のNIR吸収スペクトル強度の減少と非晶相由来の吸収強度の増加が見られた。このことは、ネック発現領域で結晶の破砕を伴う大きな構造変化が起きていることを示唆する。高密度ポリエチレン(HDPE)および低密度ポリエチレン(LDPE)の破損後の分子振動状態は、溶融状態における分子振動状態と一致し、降伏点以降の分子鎖の振動状態は非晶鎖と等しいことが分かった。直鎖状低密度ポリエチレン(LLDPE)では、破損後も分子の振動状態は非晶鎖とは一致せず、結晶中と等しい振動状態を示し、LLDPEでは球晶の破壊後も分子鎖は結晶格子中と同等の束縛状態にあることが分かった。このことから、結晶相における分子鎖の充填状態の違いによって、HDPE、LDPEでは降伏において球晶のラメラクラスターユニットへの破砕が起こるが、LLDPEではラメラクラスターユニットへの破砕に優先して結晶からの鎖の引き抜きや解きほぐれが起こっていることが分かった。A rheo-optical study has been developed to examine the nature of the structural changes, using the near-infrared spectroscopy. In this work, we investigated the strain (ε) dependence of structural changes of isotactic polypropylene (iPP) and polyethylene (PE) materials during uniaxially stretching using a rheo-optical technique ; in which the near-infrared spectra and tensile stress were simultaneously measured as a function of elongation time. It was found that the absorption coefficients of near-infrared spectra had a minimum at yield point and then reached a maximum at around the neck initiation, indicating that the main-chain motion is restricted by stretching up to the yield point. The yield point could represent the onset of the release of the molecular motion.研究課題/領域番号:16550172, 研究期間(年度):2004-2005出典：「高分子材料の破壊・破損の瞬間における分子鎖のダイナミックス」研究成果報告書　課題番号16550172 (KAKEN：科学研究費助成事業データベース（国立情報学研究所）)　　　本文データは著者版報告書より作

高分子材料の破壊・破損時における力学エネルギーの吸収機構の解明

溶液混練法により、蛍光物質をドープした高密度ポリエチレンおよびイソタクチックポリプロピレンを調製し、その延伸過程中における蛍光物質の蛍光発光挙動を応カ-ひずみ挙動と同時に測定するシステムを構築した。同時測定の結果、ポリエチレン、ポリプロピレン共に蛍光発光の波長は延伸初期から破損、ネック延伸までの測定可能であった全領域において変化しなかったものの、降伏領域において過剰な蛍光発光が観察された。この蛍光発光強度は試料中の結晶含量と相関しており、体積分率で約50%以上の結晶含量において、結晶含量の増加と共に過剰発光最が増大することを明らかにした。さらに、この過剰発光の起源を探るために降伏を起こすのに必要なエネルギーであるレジリエンスと過剰発光量の相関を調べたところ、両者は結晶含量や材料の種類によらず直線関係が得られた。このことから、降伏までに試料に蓄えられた力学的エネルギーが降伏とともに解放され、その解放されたエネルギーの一部を蛍光物質が吸収し発光していることが示唆された。また、降伏途中で延伸を中断した試料では、延伸中断後、徐々に過剰発光強度は減少していくものの、再び延伸を始めると、延伸中断直前の過剰発光強度にまで回復した。これらの知見から、材料中にドープした蛍光物質の蛍光発光挙動は、その材料の破損の程度に著しく依存しており、非破壊で試料の破損状態をモニターするためのマーカーとしての使用可能であることを見出した。In this study, we mix the fluorescent reagent which does not form the excimer into polyolefines and investigate the fluorescent behavior in the yield region in-situ during uniaxial tensile deformation. We prepare the samples with different crystallinity to reveal the effects of the structural transformation of the crystalline phases on the fluorescent behavior in the yield region.The intensity of fluorescence takes almost constant value before the yield point. The peak intensity suddenly rises up from the yield point and takes the maximum values around the central point between the yield point and the starting point of the neck propagation, so-called secondary yield point at which the neck portion appeared in the center of sample specimen. The peak intensity takes a constant value again during neck propagation. The excess emission of the fluorescence also increases with the crystallinity.The total fluorescent emission linearly increases with the resilience for the HDPE samples and the iPP samples with the crystallinity over 0.5. This result strongly suggests that the origin of the excess fluorescent emission is the release of the storage energy by the fracture of the lamellae at the yield point.研究課題/領域番号:18550188, 研究期間(年度):2006-2007出典：「高分子材料の破壊・破損時における力学エネルギーの吸収機構の解明」研究成果報告書　課題番号18550188 (KAKEN：科学研究費助成事業データベース（国立情報学研究所）)　　　本文データは著者版報告書より作

Effects of addition of hindered phenol compounds to a segmented polyurethane with shape memory on mechanical yielding

金沢大学理工研究域自然システム学系金沢大学大学院自然科学研究科The mechanical yielding behavior of the shape memory polyurethane (SMP) and its composite samples were investigated to verify the effect of addition of hindered phenol. The composite samples were prepared using SMP as matrix and hindered phenol (AO-80) as filler, and then tensile tests were carried out at a range of temperatures and with different fixed crosshead speeds. According to the tensile data at 25 °C, the yield stress was increased by adding AO-80. In terms of the Eyring theory, the activation volume of deformation units decreased with increase of the amount of AO-80 added. This is because the packing of the hard segments is enhanced by addition of AO-80. Consequently, it was suggested that the yield process is caused by the rotation of hard segment domains within the deformed plastic domains composed of glassy soft segments. © 2010 Springer Science+Business Media, LLC